Restriction syndromes

Rare causes of mechanical strabismus, usually congenital but can present later. Aka congenital cranial dysinnervation disorders (CCDD)

Differential diagnosis of mechanical restrictions

• Trauma with muscle entrapment
• Orbital mass
• Duane’s
• Tethering of optic nerve
• Restrictive myopathies
• Thyroid eye disease

Duane syndrome

• Aberrant co-innervation of LR and MR by CNIII due to pontine dysgenesis

  • Associated hypoplasia of the VI nucleus (absent on imaging)
  • Co-contraction of MR and LR

• Sporadic/autosomal dominant (10% are familial)

• F>M

• Associations

  • Cataract
  • Iris anomalies
  • Nystagmus
  • Ptosis
  • Optic disc and foveal hypoplasia
  • Marcus Gunn jaw-wink
  • Microphthalmos
  • Crocodile tears (lacrimation when eating or drinking)
  • Goldenhar syndrome (oculo-auriculo-vertebral syndrome): preauricular skin tags, Duane’s, facial asymmetry/hemifacial microsomia, limbal dermoids, vertebral column anomalies, upper lid colobomas
  • Maternal thalidomide
  • Klippel-Feil syndrome (reduced cervical range of movement, short and webbed neck, low hairline)
  • Wildervanck syndrome (fusion of neck vertebrae and deafness)
  • Limbal dermoids: occur at the interface of the sclera and cornea
  • Morning Glory Syndrome

• Often bilateral

Clinical features

• Globe retraction on adduction (due to co-contraction of MR and LR)

• Reduction of the palpebral aperture on adduction

• Up or downshoots on adduction: due to tight LR slipping over or under the globe

  • Can mimic IO overaction

• Deficiency of convergence (ie. one eye fails to converge)

• Systemic features: deafness, skeletal abnormalities and features of above syndromes

• Ocular misalignment by subtype (Huber classification)

  • 1: reduced abduction and esotropia (85% of cases)
  • 2: reduced adduction and exotropia (severe globe retraction)
  • 3: reduced abduction AND adduction, orthophoria/esotropia

• Face turn: to achieve BSV and avoid amblyopia (affects 10%)

Treatment

• Conservative: refractive, amblyopia treatment, reassurance if managing, prisms
• Surgical: for BSV and head position issues (eg. bimedial recession if esotropic and bilateral recession if exotropic). Note: LR resection will worsen globe retraction. Avoid muscle resections in Duanes.

Brown syndrome

• Mechanical restriction due to structural/developmental abnormality of the SO tendon sheath

• Produces limitation in the direction of the antagonist (IO) due to failure of SO to relax

  • So mimics an inferior oblique palsy but without superior oblique overaction

• Causes

  • Congenitally short superior oblique tendon or nodule

  • Acquired

    • Trauma
    • Surgery (eg. RD repair)
    • Inflammation eg tenosynovitis in RA or scleritis
    • Marfan’s, Acromegaly

• Improves/resolves by age 12: however congenital Brown’s rarely resolves spontaneously

Clinical features

• Limited elevation in adduction (and normal elevation in abduction)

  • Diplopiaif acquired

• Pain on attempting elevation in adduction

  • ‘Click’ (may occur during resolution)

• Minimal muscle sequelae (overaction of contralateral synergist only)

• V pattern

• Downshoot in adduction (swan dive)

• Positive forced duction test

Treatment

• Surgery if significant head posture or deteriorating binocular single vision eg. SO tenotomy. Local (retrotrochlear injection) or oral steroid for acquired cases.

Moebius syndrome

• Raresporadiccongenital
• Bilateral nuclear VI and VII nerve palsies: agenesis of the nerves
• Associated neurological abnormalities

Clinical features

• Bilateral failure of abduction: may be a pure gaze palsy or anesotropia with positive forced duction testing (due to restrictive component)

• Systemic features

  • Expressionless face
  • XII nerve palsies leading to atrophic tongue
  • Learning disability
  • Digital abnormalities: absent/small hand, syndactyly
  • Chest wall deformities: absent pectoralis muscle (Poland syndrome)

Congenital fibrosis of the EOM (CFEOM)

• Rare, non-progressive,** autosomal dominant** (CFEOM 1 chromosome 12) or autosomal recessive (CFEOM2 chromosome 11)
• Distinguished from TED by the fact it is congenital
• Normal muscle tissue is replaced by fibrous tissue
• Bilateral ptosis and restrictive ophthalmoplegia
• CFEOM1 is associated withhypoplasia of the superior division of IIIn leading to loss of elevation above the midline associated with a compensatory chin up posture

Myopic strabismus fixus

• Rare syndrome in high myopes with fibrous tightening of medial or lateral recti
• Fixed adduction/abduction with hypotropia
• MRI: deviated EOM courses and globe prolapse between the LR and SR
• Surgery can be tried